The present invention relates to an optical scanning device, and more specifically, an optical scanning device capable of reading and forming an image using a scanning laser beam.
Conventionally, in an image processing device such as a facsimile machine or digital copying machine having image reading and image forming functions, two optical systems (i.e., an image reading optical system and an image forming optical system) are provided. In a conventional image reading optical system, a surface of an original is illuminated by a light source such as a fluorescent lamp. The reflected light is directed to a sensor such as a linear CCD sensor by condenser and projecting lenses. The linear CCD sensor outputs line image data in a main scanning direction. A two dimensional image data of the original can be obtained by moving the linear CCD sensor relative to the original in an auxiliary scanning direction.
An example of a conventional image forming optical system can be found in an electrophotographic printer such as a laser beam printer. The laser beam printer has a laser emitting device, a deflector such as a polygon mirror, and a photoconductive drum. A laser beam modulated in accordance with the image data and emitted by the laser source is deflected by the polygon mirror, and is incident onto a uniformly charged circumferential surface of the photoconductive drum through an f.theta. lens. As the polygon mirror rotates, the laser beam scans the photoconductive drum in the direction of the axis of rotation of the photoconductive drum. During the scanning of the laser beam, the photoconductive drum is rotated, thereby a two-dimensional latent image is formed on the surface of the photoconductive drum. Then, toner is adhered to the latent image, and the toner image is transferred to a recording paper. The transferred image is then fixed.
However, with the above described construction, each of the optical scanning systems has a photo detector and associated hardware used for detecting the scanning laser beam at the end of each scan. This complicates the manufacturing of an apparatus using the two optical scanning systems, thereby increasing the cost of manufacturing the apparatus.